Apparatus for and method of guiding radiant energy



March 1, 1960 K. L. BELL 2,927,157

APPARATUS FOR AND METHOD OF GUIDING RADIANT ENERGY Filed Oct. 11. 1954 EXTR'MELY HIGH E4010 FKEQUE/YCY GENFAATOP l I a4 a0 38 28 40 [05) b6) J W050 MODl/t/UFD an GENE'EATOR 1 I I Tan ma RITE/Vie INVENTOR 44 Th mix/11.3011

BY WM 0. MW

ATTORNEY United States Patent Ofiice 2,921,157. Patented Mar. 1, 1960 APPARATUS FOR AND METHOD OF GUIDING RADIANT ENERGY Keith L. Bell, Washington, D.C., assignor of thirty-five percent to Robert C. Sullivan, Silver Spring, Md.

Application October 11, 1954,-Serial No. 461,583

6 Claims. (Cl. 178-75) This invention relates to' an apparatusfor and a method of guiding radiant energy, such as high frequency radio energy, and more particularly to a method and apparatus for guiding radiant energy without the use of mechanically movable elements.

Apparatus and methods presently in use for guiding high frequency radio energy usually require the use of mechanically moving antenna parts for guiding the radio frequency energy in a given desired direction. Thus, for example, conventional radar systems usually employ an antenna combination comprising a metal reflecting paraboloid and an associated movable spinner for directing transmitted pulses of high frequency radio energy to successive portions of an area to be searched or scanned. The use of mechanically movable scanning devices for variably directing'or reflecting transmittedpulses to successive portions of an area to be searched limits the scanning speedand type of lobing, and also limits the image definition and type of scan obtainable at the receiver.

It hasbeen suggested in U.S. Patent 2,391,914, issued January 1', 1946, to Raymond J. McElhannon, that a beam of radio waves may be variably reflected into space by directing the beam of radio frequency energy toward a :sheet or blanket of electrons established between a cathode and an associated end wall of a cathode ray tube. The sheet or blanket of electrons is variably deflected by suitable deflecting means to thereby changethe angles of incidence and reflection of the radio waves.

It isanobject of this invention-to provide a means for guiding radiant energy, such as high frequency radio energy, which does not involve the use of mechanically moving antenna elements.

It is a further object of this invention to provide an :apparatus and methodfor deflecting waves of high frequency radio energywith great rapidity and with great accuracy to successive portions of a predetermined area.

It is a still further object of this invention to provide a method and apparatus for guiding high frequency radio energy by an electrical, rather than a mechanical, guiding means, to'thereby avoid limitations imposed by the use of mechanically moving guide elements.

A still further object of this invention is to provide a method and apparatus for guiding high frequency radio energy which permits rapid scanning in a radar system.

vStill another object of this invention is to provide a It isstill anotherobject of this invention to provide a :method of and apparatus for guiding high frequency radio energy which may be used in projecting and reproducing a televised image in an entirely new manner :at a television. receiver.

.Still a further object of this invention is to provide anapparatus for and method "of guiding high frequency :radio energy which may be used in viewing the internal "structure of certain objects.

In achievement of these objectives, an embodiment of this invention provides a method and apparatus for guiding high frequency radio energy in accordance with which the radio frequency energy is led into a tube of the cathode ray type having a plain, uncoated face of dielectric material through which high frequency radio energy may pass. An annular or ring-shaped cathode member hav a hollow center is disposed within the tube and emits a hollow continuous stream of electrons due to its hollow ring-shaped configuration. The radio frequency energy is directed into the interior of the hollow stream of electrons emitted by the cathode member and is confined within the interior of the hollow electron stream by total internal reflection, comparable to totally reflected light in a hollow mirror tubing. The hollow electron stream is subjected to deflecting forces of conventional deflecting members, such as electromagnetic deflecting coils, with the result that the radio frequency energy contained within the hollow electron stream is deflected simultaneously in the same direction as the hollow stream of electrons, and passes outwardly into space through the uncoated radiant-energy transmissive frontal face portion of the tube. The deflected radio frequency energy may be used, for example, to scan a given desired area in a radar searchingor scanning system.

In accordance with a further embodiment'of the invention, the guided radio frequency energy may be focused onto a screen positioned externally of the cathode ray tube, the externally positioned screen being coated with a fluorescent material which becomes light emissive or luminescent upon the impingement thereon of radio frequency energy. If the radio frequency energy is' suitably modulated with a video signal prior to introduction into the hollow electron stream, the radio frequency energy striking the fluorescent coating on the external screen will reproduce thereon a television image much brighter and larger than heretofore possible in a projection system.

Further objects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawing, in which:

Fig. 1 is a schematic View of an apparatus in accordance with the invention in which the guided radio frequency energy is used in a radar system; while Fig. 2 is a schematic diagram of an embo'diment'of the invention in which the guided radio frequency energy is used in a television projection system.

Referring now to the drawing, and more particularly to Figure 1, there is shown a cathode ray tube generally indicated at It) comprising an evacuated envelope formed of glass or other-suitable dielectric material. Tube 10 has a neck portion 12 connected by a funnel portion 14 to a substantially hemispherical-shaped plain uncoated frontal face portion 15 through which high frequency radio energy'may' pass. Tube 10 is oriented vertically for transmission of high frequency radar pulses in any direction and with a linear scan as in a conventional television system. Hemispherical face portion 15 is disposed upwardly and the funnel and neck portions extend vertically downwardly. A wave guide 16 connected to a source 18 of high frequency radio energy, preferably of the centimeter, millimeter, or shorter wave-length range, is led through a suitable dielectric seal member 20 disposed in the outer end of the neck portion of the tube to maintain the vacuum in the tube, the wave guide extending a short distance into the interior of the neck portion of the tube. The dielectric material of which seal 20 is composed should be such as to readily pass the high frequency radio energy carried by wave guide 16.

A generally annular or ring-shaped cathode member 22 connected to a source of direct current electrical power 3 of the wave guide. The wave guide extends through and a short distance inwardly of tube beyond ring-shaped cathode 22 towards the energy transmissive face 15. A heater 23 connected to a suitable source of power is provided for indirectly heating cathode 22.

jCoaxially positioned within the neck of tube 10 and suitably spaced from cathode 22 inwardly of tube 10 is a hollow ring-shaped or annular-shaped first accelerating anode member 24 connected to the power supply at a point which is positive with respect to cathode 22. Anode member 24 has an inner diameter slightly greater than the outer diameter of cathode 22. The inner surface of funnel portion 14 of the tube is coated with a conductive graphite-containing aquadag coating 28, in 'a manner well known in the cathode ray tube art, to serve as a final accelerating electrode and space charge collecting anode for electrons emitted by cathode 22. Aquadag coating 28 is connected by conventional means to a point on the power supply which is substantially more positive than the positive potential of anode 24.

Conventional electromagnetic deflecting coils diagrammatically indicated at 30 and 32 which respectively pro- .vide a horizontal and vertical deflection of the hollow electron stream according to the deflection frequencies applied to these coils, are positioned adjacent the junction of the neck and funnel portions of the tube. Conventional focusing means indicated at 34 may also be employed.

Due to its ring-shaped configuration, cathode 22 will emit a continuous stream of electrons indicated at 36 which is of substantially hollow cylindrical or tubular shape. This hollow stream 36 may be deflected with great rapidity to any point on the hemispherical energy transmissive face 15 of the tube by the horizontal and vertical deflecting coils 30 and 32 in accordance with conventional methods well known in the art. Electron stream 36 will preserve its hollow cylindrical shape during its deflection by coils 30 and 32. The high velocity of the electrons in the hollow electron stream, as well as their own electromagnetic field and spin effect, minimizes any tendency to deformation of the shape of the hollow electron stream which may be caused by electromagnetic forces exerted on the side walls of the stream by the contained high frequency radio energy. Furthermore, any tendency to deformation can be controlled by adjustment of the potentials on the focusing means 34 and on the accelerating electrodes 24 and 28 to thereby increase the velocity of the electrons in the hollow electron stream, to thereby aid in maintaining the shape of the stream.

Since the wave guide 16 is coaxially positioned with respect to and passes through and slightly beyond ringshaped cathode 22, the radio frequency energy from wave guide 16 passes into the interior of the hollow stream 36 of electrons. Furthermore, the high frequency radio energy is confined within the hollow interior of the electron stream 36 by total internal reflection, so that whenever the hollow electron stream 36 is deflected by the deflecting means 30 and 32, the contained radio frequency energy within the hollow electron stream will be simultaneously deflected and guided in the same direction as that in which the hollow electron stream itself is deflected.

The dimensions of the hollow central area of cathode 22 and consequently the dimensions of the hollow cross sectional area of hollow electron stream 36 should be proportioned relative to the wave length of the radio frequency energy to be guided in accordance with the well known principles established for wave guides. (See Principles of RadarM.I.T. Press-McGraw-Hill Book Co., 1952, page 546.)

The high frequency radio energy which is guided in accordance with the deflecting forces applied to the hollow electron stream 36 will pass freely out through the plain, uncoated front face 15 of tube 10 and into the space beyond face 15, where the high frequency radio energy may be used, for example, in scanning or searching a given area, as in a radar system. By proper control of the deflecting voltages applied to deflecting coils 32 and 34, the beam of high frequency radio energy may be directed through any point on the hemispherical face (15 of the tube. When tube 10 is vertically oriented, as shown in Fig. 1, linear scanning through a wide spherical are, as determined by the limits of practical deflection, may be accomplished.

In using the hereinbefore described apparatus and method in a radar system, vertical and horizontal scanning frequencies employed at the radar transmitter are also employed at the radar receiver, the scanning at the transmitter and receiver being synchronized in a conventional manner to thereby resolve a received image in gradation comparable to a television image.

A further application of the method and apparatus of the invention is shown in Figure 2 which shows a tube 38 comprising an evacuated envelope of suitable di electric material having a plain, uncoated frontal face 39 with a slight curvature similar to that of a cathode ray tube used in a conventional television receiver. Face 39 permits transmission therethrough of high frequency radio energy. Disposed within the neck portion of the tube are a ring-shaped cathode 22', a ring-shaped first accelerating anode 24, and a heater 23' for indirectly heating cathode 22. An aquadag coating 28', suitably connected to a positive point on the power supply, is disposed on the inner surface of the funnel portion of the tube to serve as a final accelerating electrode and space-charge collecting anode. Horizontal and vertical magnetic deflecting coils 30' and 32 surround the neck of the tube. Focusing means 34' are also employed. All of the elements just described are similar to and function similarly to the corresponding elements of the embodiment of Figure 1-.

A coaxial cable 40 is led through a suitable radio energy transmissive dielectric vacuum seal into the interior of the neck portion of tube 38 where the coaxial cable 40 is surrounded by ring-shaped cathode 22'. Coaxial coriductor 40 is connected to a source of high frequency radio energy in the form of a radio frequency oscillator 42 which generates high frequency radio waves, preferably of the centimeter, millimeter or shorter wave-length range. Oscillator 42 is connected to a source 44 of video signals in such manner that the output of oscillator 42 is modulated in accordance with the video signals received from source 44. A screen 46 having a coating 48 of a fluorescent material which becomes light emissive when impinged upon by high frequency radio energy, is disposed in spaced relation to the outer or frontal face 39 of tube 38. Coating 48 may be formed, for example, from a composition in the activated sulphide group, or from the group of alkaline earth halide salts. Compositions from the groups just mentioned are known to fiuoresce under excitation by high radio frequencies. A dielectric lens 50 or other suitable focusing means for high frequency radio energy is disposed intermediate the face 39 of tube 38 and screen 46 and is employed to focus the radio frequency energy upon screen 46.

Ring-shaped cathode 22' emits a continuous hollow stream of electrons in the manner previously described, and this electron stream is deflected in the same manner previously described by the horizontal and vertical deflecting means 30' and 32'. Deflection of the hollow electron stream 36' causes the confined radio frequency energy to be deflected simultaneously and in the same direction as the hollow electron stream in the manner previously explained. The deflected radio frequency energy passes outwardly through the plain, uncoated face 39 of the tube. The radio frequency energy passing outwardly through face 39 is intercepted by the dielectric lens 50 and brought to a focus on screen 46. Radio frequency 839" impinging upon the fluorescent coating 48 of screen" '46 causes the fluorescent materi l" to luminesce. Thevolta'ge's applied to the horizontal and vertical deflecting means '30 and 32' are synchronized in the well known manner'with the synchronising signals of the television transmitting station so' that the hollow stream 36' is scannedhorizontally and vertically as in the conventional television receiver. Hence, the contained radio frequency energy within the hollow electron stream 36' may be deflected in a scanning action both horizontally and vertically onscreen 46 to produce an image on the fluorescent coating 48 in accordance with the transmitted video signal.

The apparatus and method of the invention as illustrated in the embodiment of Figure 2 may also be utilized, if appropriately modified, to view the internal structure of certain objects, such as the human body, for example.

The object whose internal structure is to be observed should be placed intermediate the frontal face portion 39 of the tube and the fluorescent screen 46. The radiant energy, such as high frequency radio energy, passing through the frontal face portion of the tube is brought to a focus in the plane of the object by a dielectric lens or other suitable focusing means disposed between the frontal face of the tube and the object. A second dielectric lens is interposed between the object and fluorescent screen 46 to bring the radio frequency energy at the plane of the object to a second focus on the fluorescent screen.

The radio frequency energy is scanned vertically and horizontally as in the projection of a television image, as described in connection with the embodiment of Figure 2. However, the radio frequency energy, instead of being modulated with a video signal, as in the case of the embodiment of Figure 2, is unmodulated, and is maintained at a constant signal amplitude. Thus, the transmission of the radio frequency energy to the fluorescent screen is modified only by variations in the transmission characteristics of the object interposed in the path of the radio frequency energy on its way to the fluorescent screen. For example, if the interposed object is a human body, the bone structure of the body modifies the passage of the radio frequency energy and thus modifies the degree of fluorescence at screen 46 to thereby provide a visual indication of the internal structure being observed.

While an annular ring-shaped cathode has been described in the various embodiments of the invention as the source of the hollow electron stream, to thereby provide a hollow electron stream of cylindrical cross section, this has been merely by way of example. The cathode may instead be of hollow rectangular or hollow oval shape, for example, so as to emit a hollow electron stream of corresponding shape in cross section.

It can be seen from the foregoing that there is provided in accordance with this invention a method of and apparatus for guiding radiant energy, such as high radio frequency energy, which requires no mechanically moving parts and which permits deflection of the radio frequency energy substantially instantaneously as desired. The method and apparatus hereinbefore described may be used in transmitting search pulses in a radar system without requiring the use of mechanically movable antenna elements as has heretofore been the practice. The apparatus and method of the invention permit linear scanning in a radar system similar to that used in conventional television scanning. Furthermore, the method and apparatus for guiding high radio frequency energy may be used in a television receiving system to project a television image externally of a cathode ray tube in a manner which will provide much larger and brighter television images than has heretofore been possible in projection systems. The method and apparatus of the invention may also be used to view the internal structure of objects such as the human body.

While there have been shown and described particular embodiments of the invention, it will be obvious to those 6 skilled in"the art'tha't various chahges'ahd'jmodiflcations may bemade' therein without'departing, from the invention and; therefore, it isainied to cover all such changes and modifications a's'fall within the true spirit and scope of the invention.

What I claim as my invention is:

1. An apparatus for projecting a television image comprising, in combination, a source of radio frequency energy, means for modulating said radio frequency energy with a video signal, means for producing: a hollow stream of electrons, meansfor introducingthe modulated radio frequency. energy into the hollow interior of said hollow stream of electrons, means for deflecting said hollow stream of electrons to therebycorrespondingly deflect the modulated radio frequency energy within said stream of electrons, a screen disposed in the path of said modulated radio frequency energy, said screen being coated with a fluorescent material which becomes activated when excited by radio frequency energy, said modulated radio frequency energy exciting said fluorescent coating to thereby produce a television image on said coating.

2. An apparatus for projecting a television image comprising, in combination, a source of radio frequency energy, means for modulating said radio frequency energy with a video signal, an evacuated dielectric envelope having a frontal face portion which passes radio frequency energy, means disposed in said envelope for producing a hollow stream of electrons, means for introducing the modulated radio frequency energy into the hollow interior of said hollow electron stream, means for defleeting said hollow stream of electrons to thereby correspondingly deflect the modulated radio frequency energy within said stream of electrons, a screen disposed exteriorly of said envelope, said screen being coated with a fluorescent material which becomes activated when excited by radio frequency energy, said modulated radio frequency energy passing through the frontal face portion of said envelope to excite said fluorescent coating and thereby produce a television image on said coating.

3. An apparatus for projecting a television image comprising, in combination, a source of radio frequency energy, means for modulating said radio frequency energy with a video signal, means for producing a hollow stream of electrons, means for introducing the modulated radio frequency energy into the hollow interior of said hollow stream of electrons, means for deflecting said hollow stream of electrons to thereby correspondingly deflect the modulated radio frequency energy within said stream of electrons, a screen disposed in the path of said modulated radio frequency energy, said screen being coated with a fluorescent material which becomes activated when excited by radio frequency energy, and means for focusing said radio frequency energy onto said screen, said modulated radio frequency energy exciting said fluorescent coating to thereby produce a television image on said screen.

4. The apparatus as defined in claim 3 in which said means for focusing said radio frequency energy is a dielectric lens.

5. An apparatus for projecting a visual image in accordance with a modulated signal comprising, in combination, a source of radio frequency energy, means for modulating said radio frequency energy, means for pro ducing a hollow stream of electrons, means for introducing the modulated radio frequency energy into the hollow interior of said hollow stream of electrons, means for deflecting said hollow stream of electrons to thereby correspondingly deflect the modulated radio frequency energy within said stream of electrons, a screen disposed in the path of said modulated radio frequency energy, said screen being coated with a fluorescent material which becomes activated when excited by radio frequency energy, and means for focusing said radio frequency energy onto said screen, said modulated radio frequency energy exciting said fluorescent coating to 7 thereby produce a visual image on said screen in acoordance with the modulated radio frequency energy.

6. An. apparatus for projecting a visual image in accordance with a modulated signal comprising, in combination, a source of radio frequency energy, means for modulating said radio frequency energy, an evacuated dielectric envelope having a frontal face portion which passes radio frequency energy, means disposed in said envelope for producing a hollow stream of electrons, means for introducing the modulated radio fi'equency energy into the hollow interior of said hollow stream of electrons, means for deflecting said hollow stream of electrons to thereby correspondingly deflect the modulated radio frequency energy within said stream of electrons, a screen disposed exteriorly of said envelope, said screen being coated with, a fluorescent material which becomes activated when excited by radio frequency energy, said modulated radio frequency energy passing outwardly through the frontal face portion of said envelope to excite said fluorescent coating to thereby produce a visual image on said screen in accordance with the modulated radio frequency energy.

References Cited in the file of this patent UNITED STATES PATENTS 

